The present invention relates generally to a computer controlled electrolyte polishing (electropolishing) system for analytical research.
Electrolytic polishing (electropolishing) can be a useful metallographic specimen preparation technique when properly applied. Electropolishing can remove the mechanical deformation induced from cutting and grinding the specimen resulting in a surface that is unworked from the polishing procedure. For some metals electropolishing can produce a surface finish that is equal to or better than the finish obtainable by mechanical polishing methods. electropolishing technique that yields results for all metals has not been found (See G. F. Vander Voort, Metallography Principles and Practice, McGraw-Hill, New York, pp. 119-125 (1984)). The conditions and electrolytes required to obtain the desired surface finish differ of different alloys. There is a wide variety of literature available suggesting electropolishing procedures for various metals, however, the same results are not always achieved when attempting to duplicate these experiments. In addition, developing electropolishing techniques for new alloys using traditional methods requires a considerable amount of time. Other types of sample pareparation (i.e. mechanical) are often employed due to the time consuming and tedious nature of establishing electropolishing procedures.
Using traditional electropolishing techniques, before electropolishing the metallographer must choose the electrolyte composition, the electrolyte temperature, cathode material, anode/cathode area ratio, anode cathode separation, type and degree of agitation, etc. Available literature recommends appropriate parameters for most applications (See "Metallography and Microstructures," Metals Handbook Ninth Edition, American Society for Metals, Cleveland, Ohio pp. 48-56 (1985); and Vander Voort cited above) The polishing region must then be determined for the given set of conditions. This is accomplished by manually varying the voltage on the power supply and monitoring the current until a stable reading is obtained.
FIG. 1 shows the type of plot commonly obtained when using an electrolyte that forms an ionic film on the specimen surface during polishing. Etching occurs at low voltages between (a) and (b); polishing occurs in the Plateau region between (c) and (d); and gas evolution and pitting occurs between (d) and (e) (See Vander Voort, cited above).
Manually generating this characteristic curve while controlling and monitoring the other parameters is a tedious and time consuming task. Also, the curve might reveal that the selected conditions are not suitable for the particular application. This means that the curve must be plotted again for a new set of conditions.
There are U.S. patents of interest in the chemical art relating to the of use of electrolysis for the erosion of a workpiece for shape or surface change; e.g., etching, polishing. etc. U.S. Pat. No. 4,705,611 to Grimes et al is concerned with a method for electropolishing tubes, and U.S. Pat. No. 4,372,831 to Rosswag discloses electrolyte solutions for electropolishing. These patents do not include any suggestion for the use of a computer.
In the electrical computer and data processing art, applications for product manufacturing by machining, there are a number of patents relating to numerical control. Munekata et al (U.S. Pat. No. 4,513,366) disclose a menu programmed machine tool numerical controller operated by a microprocessor connected to a data input device, a CRT display, and data storage. The microprocessor makes various tool and tool path calculations and displays messages on the CRT screen. In Hoch et al (U.S. Pat. No. 4,446,525) a numerical control system executes part programs. A parameter table containing parameter values evaluates parameters and arithmetic expressions during the execution of a part program, and parameter values may be changed by part program instructions or manual data entry. Tanaka (U.S Pat. No. 4,591,989) is concerned with a numerically controlled machining system which stores in a memory a machining program having matching pattern commands for specifying machining patterns, tool commands for specifying tools, and positional information commands for specifying positional information for the tools, Ichikawa (U.S. Pat. No. 4,556,957) shows a numerical control system which includes a display device, a display control device, a data setting device, a memory, a computer, a central processor, and an control device. These patents do not include any suggestion relating to the use of a computer for electropolishing, etching, etc.